Porous Dielectric Structure and Response Speed of Moisture Sensors

We made moisture sensors using α-Al2O3 films as porous dielectric materials deposited through the anodic spark deposition (ASD). In this study, a variety number of small pores has been studied to investigate the response speed of moisture sensors. Three different surface morphologies have been studied using scanning electron microscopy (SEM). Sample DM23 has the maximum number of small pores. Small pores are defined as pore size ranging from 40 nm to several hundred nm. Sample TA40 has the minimum number of small pores. Sample FW06 has the medium number of small pores. We found that the sensor made from dielectric material with the maximum number of small pores has the fastest response speed, and that from the minimum number of small pores has the slowest response speed either from high humidity to low humidity or from low humidity to high humidity.